Ten structures were reportedly considered threatened by the fire Tuesday morning, but that mention was removed from online fire information later in the day.

One backcountry yurt in the Whoopum-Up recreation area on the west side of Idaho 21 is "pretty close to the fire," Susan Blake of the Boise National Forest said Tuesday. Other structures near the fire include mines, she said.

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The area is closed to cars and campers, but it isn’t keeping people out, Blake said.

"There's a lot of incursions into the closed areas by ATVs and OHV (off-highway vehicle) enclosed vehicles,” she said, urging people to stay out of the fire closure area for their own safety.

“The public could really help us out by staying out of those closed areas, because if something happened, we wouldn't know,” she said, adding that nearly 70 incursions have been reported.

The Boise County Sheriff’s Office is trying to monitor likely entrances and keep people out, but they can’t be everywhere at once, Blake said.

It’s burning about eight miles north of Idaho City. The fire’s growth prompted officials to close a section of Idaho 21 Tuesday morning, among other reasons to possibly use part of the highway as a fire control line.

Crews Tuesday were removing trees and brush from along nearly 25 miles of the highway — from milepost 72.5 north of Lowman near the South Fork Lodge, to milepost 48 one mile west of Ten Mile Campground — “while still maintaining the scenic drive nature of the road,” according to a Forest Service press release.

This week’s hot weather is complicating matters, the Forest Service noted, and flames could keep spreading north and east.

More than 850 personnel are working on the fire using 10 helicopters. Twenty-one engines are one scene with four bulldozers and nine water tenders.

“As the fire spreads it is anticipated that the smoke will continue to be seen throughout a large area including Boise, Cascade, Lowman and beyond,” the Boise National Forest news release continued. “Firefighters are making good progress in securing the southern and southeastern flanks of the fire in order to protected the Elk Creek drainage, which is the main source of drinking water for the community of Idaho City.”

Area closures have expanded to include all forest roads east of Grimes Pass Road, west of Road 312, north of the North Fork of the Boise River and south of Idaho 17.

Community meetings were held in Idaho City Monday evening and Lowman Tuesday to inform community members and answer questions.

The area’s other recent large fire, the Mile Marker 14 Fire, which burned more than 4,300 acres on both sides of Idaho 21, is classified as 100 percent contained but still producing smoke visible from the highway. And the Robie Creek boat launch at Lucky Peak, closed last week to make it easier and safer for firefighting helicopters to dip water from the reservoir, has reopened.